Testing FTTH network is similar to other OSP testing but the splitter and WDM add complexity. FTTP PON networks can be more complicated than simple OSP links, with WDM couplers, PON splitters, etc. in a single link, so complete testing can include some components and installation issues not familiar to the usual OSP tech. PON couplers add high loss, WDM couplers have different performance at different wavelengths and connector reflectance, not a problem in most systems, can be a problem in short links typical in FTTx. Many FTTx systems use APC (angled PC) connectors to reduce reflectance so test cables for both OLTS and OTDR need to have matching connectors.

    However, once installed,  users on a live network means testing cannot disrupt service. Thus testing may be as simple as checking power at the ONT on the subscriber’s house with a calibrated fiber optic power meter or just seeing if the ONT has a “green” connection light! The ONT at the home usually has some intelligence that can be accessed from a remote location, allowing a service tech to initiate a loopback test to verify connections at any user. If only one user has a problem, a service tech is then sent there, while if all users are down, the tech is sent to the central office.

   As with most fiber optic links, troubleshooting requires knowing the architecture of the system, expected link losses and optical signal levels and typical problems that may be encountered. As always, we emphasize the importance of having documentation on the system before testing and troubleshooting.